This invention relates to a throttle valve control apparatus in an internal combustion engine mounted on a motorcar or the like.
Known throttle valve control apparatuses for instance, as shown in Unexamined Publication Showa 54-74824 of Japanese Utility Model Application, can be provided with an automatic idle speed increasing means for causing a throttle valve, in the intake passage of the engine, to open beyond a predetermined idling position according to the increase in engine load caused by use of an air cooler, a lamp or the like in order to prevent the engine from stalling. Additionally, there has been known also, for instance, in Japanese Patent Publication Showa 56-13177, throttle valve control apparatus provided with a valve closing means for closing the throttle valve in the intake passage of the engine beyond a predetermined idling position when the valve is closing at the time of deceleration, descending of a slope or the like in order to improve the fuel economy of the engine and protect the exhaust gas purification catalyzer. Of course, both of the foregoing two means can be provided in the same apparatus.
If, in such a case that both means are provided, the two means are simultaneously operated at the time of deceleration when using an air cooler or the like, it is usual that the throttle valve is subjected only to the operation of the idle speed increasing to be opened beyond the idling position, whereby disadvantages in respect of fuel cost economy, catalyzer protection, engine brake effect, etc. are caused.
The idle speed increasing means is not required to be operated when the engine is subjected to torque from the driving wheel side at the time of deceleration, descending of a slope or the like, and accordingly it is desirable, in such a case that the two means are provided, that the operation of the idle speed increasing means be restrained at the time of operation of the valve closing means.